I have been hiking and backpacking for the past twelve years, going on the occasional overnighter or day hike. In the past three years, I have begun night hiking and long day hikes (twenty miles [32 km] or more) with an emphasis on light weight, speed, and bagging peaks. These trips center on Washington's Central Cascades (terrain characterized by steep inclines and "moist" conditions). I am not a fair weather hiker, so I inevitably tromp through the rain and snow we experience in the Pacific Northwest.

I am a utilitarian. Given that premise, I expect my gear to be free of frills -- unless those frills have merit on the trail. The Atmos includes several frills, including the fabrics: 210D Twill Velocity Cordura® and 160D x 210D Window Ripstop Cordura®. These materials are strong but lightweight, qualities which have merit during my ultralight overnighters. The other frills are described below:- Two options for hanging a hydration reservoir -- one inside the main compartment and one in the "dead space" between the mesh of the back panel and the fabric of the main compartment.- An AirSpeed suspension system (an aluminum hoop frame with a mesh backpanel that creates a space of air between where my back contacts the mesh and the actual material of the pack).- A stow-on-the-go pole attachment system. This system uses two elastic cords with a plastic sheathing on each. The rear cord is on the outer left side of the pack. Insert the "basket" end of the poles into it. The front cord is attached to the left shoulder strap and includes a cinching device to prevent the poles from swaying. Insert the handles through this cord.- Two waist belt mesh pockets with zippers.- One large adjustable stretch woven front pocket with a clip at the top.- Two side stretch woven pockets (with compression straps to secure the load).- Dual tool attachments and bungee tool tie-offs. - Removable sleeping pad straps with clips for quick retrieval of the sleeping pad.- Two zippered "slash" pockets, one with a mesh interior. I define a "slash" pocket (Osprey's terminology, not mine) as having one entry point at the top that opens into a small compartment. The mesh lined pocket measures approximately 12inX9inX3in (30cmX23cmX7cm), while the other pocket measures approximately 10inX10inX4in (25cmX25cmX10cm). Because these pockets are sewn in on either side of the main compartment, their expansion does cut into the space available within that main area.- Zippered access to the main compartment. These zippers do not flow down to the bottom of the pack, so squeezing in oversized items may prove an issue.

It does not come with a rain cover, though Osprey does make covers for the Atmos series. Wet seasons around the Pacific Northwest last nine months out of the year, so this may prove a necessary investment.

READING THE INSTRUCTIONS

Like most packs I've purchased in recent years, the Atmos came with directions . . . very thorough directions. Most of the directions refer to actions that I found rather intuitive - using the stow-on-the-go system, rerouting the compression straps, and manipulating the bungee tool tie-offs. In fact, I figured out how to use the features before I even looked at the directions. The directions come with plenty of pictures labeling the parts of the pack that correspond to the instructions for each component. If intuition proves a fickle guide, the directions are specific.

TRYING IT OUT

The stow-on-the-go system quickly keeps my poles, when collapsed, close to my body and out of the arc of my arm movement . . . as long as I'm standing in my living room. I have yet to try it out on the trail. I'm concerned that the way the poles stick out in front and in back of me will make this storage option impractical for scrambling.

Compression straps within the side stretch pockets (in the form of a Z) and one towards the top of both sides quickly deflate the pack. The side stretch pockets are not fully enclosed at the bottom, making them more like fabric panels than pockets. I find this feature puzzling because it limits these two pockets to stowage for solid objects like water bottles but not looser necessities like a compass or a fold map. I anticipate some annoyance that the top compression straps add two more steps to getting into the main compartment, though I understand their importance in securing loads to the side of the pack. I was worried that the narrowness of the waist straps would feel awkward, but my worries proved unfounded -- it fits comfortably and is easy to adjust.

I successfully fit a pair of shoes (size 7.5 US) or a climbing helmet (size large) in the front stretch pocket (see pictures below). Squeezing the shoes in took some patience and small adjustments, but the helmet slid in with ease.

Because my overnight backpacking style fits the ultralight category, I use a ¾ size sleeping pad, which easily fit between the two sleeping pad straps (see pictures below). Despite the short length, these compression straps kept the pad in place. I doubt that even some brushes by tree branches would dislodge it.

I filled the main compartment and two slash pockets with the rest of my ultralight arsenal (a sleeping bag, two jackets, a headlamp, a hat, an emergency kit, a compass). The slash pockets seemed like fathomless wonders, expanding to fit the small stuff. I plan on using the "non-mesh" pocket for any electronics I bring because it seems a bit more insulated from the elements. The zippers for the slash pockets and the main compartment have a fold of material over them for extra protection from the elements. The zipper pulls themselves have a half-circle plastic sheath that makes them easy to grab and noiseless during movement.

I stuffed some food, mainly energy bars, into the waist belt pockets. It easily holds four per pocket. The zippers do not easily open with one hand while wearing the pack, but it is not difficult to "start" the zipper with two hands. The open mesh of the pockets is nice in that I can see what I've stowed in each, and the holes of the mesh are small enough that loose items won't slip through.

My water reservoir fills the entire length of the internal pouch and securely hangs from the strap intended for such use. The portals for the tube are tight but big enough. Threading the tube the rest of the way through the two elastic straps on the shoulder straps is easy. I can easily place the tube in my mouth without having to bend my head down uncomfortably.

I don't have an ultralight tent, so I doubted that my three season, four-person tent would fit . . . but it did, even with the rest of my gear. Was it a tight fit? Yes. The size of the tent caused the material to bulge a bit at the bottom of the main compartment, but this bulge did not affect the fit. I credit this comfortable fit to the space between the mesh backpanel and the actual material of the pack (what Osprey calls the AirSpeed suspension), for the bulge only extended into this dead space.

Wearing the pack with this mock up surprised me due to the AirSpeed suspension. It places the center of gravity of the pack in a different place than I'm accustomed - not bad or disorienting, just different. After some fiddling with the pack's placement, the difference was negligible. Trail testing will determine if this difference remains negligible. I was delightfully surprised by the pack's placement in relation to my head, for it did not limit my full range of motion.

In order to weigh the pack, I had to use it as my bag during my bike commute. Obviously, this pack is not designed for such movement, so I was not surprised that the hip belt's location caused the pack to sway a bit as I pedaled. But my commute is long enough that I worked up a bit of a sweat. The mesh panel did allow my back to breathe more than I'm accustomed to. I also adjusted the shoulder straps on the fly with one hand and moved my helmeted head without butting against the top of the pack. This last fact surprised me in that the angle of my back in relation to the back of my head seemed destined to pose problems.

SUMMARY

The Atmos includes features I'm skeptical I'll really need, like the stow-on-the-go system. Fortunately, I enjoy adding new options to my hikes, even if it means converting from skeptic to evangelist. The sheer volume seems ideally suited to the overnighters I fit into my schedule . . . not too big, not too small. The Atmos includes accoutrements I already consider standard on my packs: waist belt pockets, stretch fabrics, easy-to-use zipper pulls, and comfortable straps. But only the trail can reveal if the Atmos's version of these features works well.

This concludes my Initial Report. The Field Report will be amended to this report in approximately two months from the date of this report . Please check back then for further information.

It seems I always have grand plans for testing products that become dreams in light of the reality of my schedule. Not so with this test. I experienced some epic places in Washington State during the field testing phase: Silver Peak, The Enchantments, and Bandera Mountain.

Silver Peak has fast become one of my favorite places for a quick overnight trip. It rests in the central Cascades and tops out at 5605 ft (1708 m), placing the upper section above the tree line. The first mile and a half (2.5 km) follows the Pacific Crest Trail, a well maintained path that gradually ascends (minimal elevation gain) within a dense canopy of trees with some boulder fields. From here the trail climbs steeply, following a creek. This close location makes the trail mushy and unstable at times. There is one section in which we had to scramble up a small rock outcropping. The last half mile (0.8 km) is essentially a scree field that transitions to a low class scramble, ending our 1000 feet (305 m) of elevation gain. At the point of this transition there is a little cluster of wind-beaten trees with just enough open space to warrant pitching a tent. We made our approach at night in 45 F (7 C) weather with clear skies. As so often happens in the Pacific Northwest, clouds rolled in as we slept, soaking our tent and us during the descent the next morning. It made some sections that were mushy during the ascent slick during the descent.

The Enchantments had been on my bucket list since I had heard of them over ten years ago. Overnighting in the area requires a reservation - spots are not easy to come by. But trekking through the area - 18 miles (29 km) round trip - in one day comes with no stipulations (except the stamina to complete the route). Our route entailed over 5000 feet (1524 m) of elevation gain and 6500 feet (1981 m) of elevation loss, topping out at around 8500 feet (2591 m) above sea level. The ascent bears the endearing nickname "The March of Death," mainly due to one section's elevation gain of over 2000 feet (610 m) in just one mile (1.6 km) in a boulder field known as Asgard Pass. Most of this ascent occurred in a light snow (none of it accumulated) and temperatures in the low 30s F (-0s C).

The Enchantments derive their name from the picturesque high alpine lakes and tundra-like turf at the top. Our trip added to this splendor frozen waterfalls near the top (see the first picture below). Everywhere I looked a view of cragged peaks met my eyes (see the second picture below for a sampling). I found the nickname attributed to the ascent better described the 12 mile (19 km) descent - it seemed it would never end as we meandered through dense tree cover and the occasional lake, tramping over worn dirt trails. My blister-free feet rejoiced at the sight of the parking lot; my eyes longed for more time at the top to take in the unrivaled uniqueness.

Bandera Mountain, like Silver Peak, rests in the Central Cascades, topping out at 5300 feet (1615 m) above sea level and seven miles (11 km) of trail round trip. The trailhead begins at 2200 feet (671 m). New improvements make this trail plush - more trail side vistas than any trail I have literally ever encountered, gravel pathways through boulder fields, and carefully set rock steps. At 4300 feet (1311 m) the trail to Bandera makes a decided turn to the top in a direct line. The result is a grueling final 1000 feet (305 m) of scrambling and hiking. We made our ascent and descent in the dark, sneaking this hike in while our families slept. Temperatures in the low to mid 30s F (-0 C) resulted in ice-covered rocks and trees at the top.

PERFORMANCE IN THE FIELD

The Atmos is designed for light weight overnighters and day trips. Keeping that in mind during my excursions in the field testing phase, I made the following observations:

Silver PeakThough the pack is not waterproof, my gear was not wet at all (the amount of rain that fell was so great that if it was going to get wet, it would have been). My light weight overnight gear - a 32 F (0 C) sleeping bag, sleeping pad, emergency clothes, some bars for food, and my portion of the tent (a bulky three season, four-person tent) -- all fit easily. The stow-on-the-go pole feature does not work well while scrambling - the poles have a tendency to bump into the rock face, which could throw off a person's balance at a crucial moment (though I only found it annoying). Cramming gear into the main compartment does decrease the "dead space" of the Air Speed area at the back panel, but this decrease does not affect the comfort of the pack. I found the overall fit to ride nicely during hiking, despite the fact that my center of gravity was a bit farther back than I'm used to with a backpack. I especially like having a full range of motion with my head during the ascent. Looking up while wearing an overnight pack has never been so easy.

The EnchantmentsI packed for a day trip (extra clothes, a full 100 ounce [3 L] water reservoir, plenty of food, poles) with some emergency gear (an ice ax, traction devices). The Atmos effortlessly swallowed all of it. The ice ax holder works well. The bungee for securing it at the top is easy to use and it remains snug. I did, however, make the mistake of attaching it with the "teeth" pointed outwards, which resulted in the occasional snag on a passing branch. I had some issues with the waist belt. I think I had it too loose, which resulted in some abrasions around my waist, though I was not aware of the abrasions until after the hike. There was plenty of space for food when I utilized one waist belt pouch and one of the slash pockets. In fact, I had hidden food so effectively that I forgot one cache until the end of the hike. I kept my camera in the other waist belt pocket. It was not easy to retrieve the camera from its case when in the waist belt pocket. I eventually kept just the camera in this pocket, despite the chance it would get hit. My frustration stemmed from working the zipper with one hand - I had to hold the zipper's path taut with one hand and pull with the other hand.

Bandera MountainThe stow-on-the-go pole feature is still not without issues during scrambles, bumping into the rock face. Aside from that issue, I got used to having the poles stowed while hiking. I used a 70 oz. (2 L) water reservoir instead of my usual 100 oz (3 L), which did not extend to the bottom of the pouch in the inside of the main compartment - the hook at the top still kept it in place. Though this hike was much shorter than the Enchantments, I experienced some movement around the waist again despite having cinched it tighter. I assume that, had this trip been long, the abrasions around my waist would have returned. As it was, they did not. I love the decreased sweat build up on my back that results from the Air Speed feature - I did not get a chill on my back when I removed my pack.

SUMMARY

The Atmos lives up to my basic expectation: it comfortably holds all of my gear, regardless of the trip type. But this comfort level does not score a ten out of ten, mainly due to the movement of the waist belt during long trips. The extra features have merit. If I were hiking alone, I would appreciate the stow-on-the-go pole feature for the ease with which I could transition from one hiking technique to another . . . as long as I didn't have to traverse a difficult scramble. The Air Speed "dead" space does increase ventilation and make the pack more comfortable in that I don't ever feel any of the pack's contents protruding into my back. The waist belt pockets are convenient, especially when compared to the alternative of taking off the pack in order to access a quick treat. But they are not so convenient that I can open them while moving because they require the use of both hands. At this point in the testing phase, I consider the Atmos preeminent among my arsenal of packs, despite its limitations.

Things I Like- comfortable fit- ample room for my gear- the Air Speed back panel

Things I Don't Like- having to use two hands to open the waist belt pockets- scrambling with the poles in the stow-on-the-go position

The long-term testing phase found me staying close to home, haunting some familiar trails and one newly discovered gem over the course of 28 miles (~37 km) during three separate hikes.

Mt. Washington has made it into a few of my past testing series. The trail, like most in the central Cascades, is a mixture of roots, rocks and dirt . . . with the occasional scree field or snow chute to liven it up. With 3400 ft (~1000 m) of elevation gain in twelve miles (19 km) -- a distance my friends and I debate every time we hike it because no map we've seen gives an accurate reading of the new "trail" to the top -- the mountain offers a challenge. In fact, I've come to loathe the lower section with its ankle-turning loose rocks. This particular trip had its fair share of snow, too. Six of us took turns postholing through the three feet (~90 cm) of snow that blanketed the last 1000 feet (~300 m) of elevation gain in temperatures just above freezing and visibility that varied from zero at the mid-point to clear at the top. In the end, a trip that usually takes three hours round trip took nearly five.

Another stock hike of mine is Squak Mountain. I sought variety by traversing the peak, a seven mile (11 km) route with 1500 feet (~450 m) of elevation gain and 1800 feet (~550 m) of elevation loss. Temperatures in the mid-40s F (~4 C) and a light rain prompted me to overdress and quickly overheat. The trail itself is well maintained and characteristically steep for the central Cascades.

My new discovery (new only to me) goes by Otter Falls. Low snow levels prompted me to forego any peak bagging because my larger goal was an overnighter. Otter Falls rests at the end of a 4.5 mile (7 km) hike with minimal elevation gain. Though I wasn't looking for a challenge, the conditions provided one. Snow on the ground two miles (3 km) in, constant rain, and no less than ten substantial creek washouts made this night entry interesting. I kept plodding along, picking my way over swollen streams in the dark, because I knew that in the light I would laugh at anyone who turned away from what I was sure were easily passed waterways. The next morning's return proved me right. The return, however, offered a new challenge: the snow had melted and turned to ice. Although I didn't fall at any point, I did find myself precariously close to doing the "splits" in an effort to stay upright. Did I mention it rained non-stop? Regardless of the dangers, real or imagined, Otter Falls proved an impressive sight (see the picture below).

Otter Falls in the early light.

PERFORMANCE IN THE FIELD

I've debated since the test series began whether or not I should invest in a rain cover. Unfortunately, the completion of the test series finds me ambivalent still. Why? The Atmos does not repel rain, nor does it provide zero protection against rain. Instead, it allows some moisture to enter its various pouches and pockets during the extremely wet conditions I encountered during my Squak Mountain and Otter Falls trips. On an overnighter like my trip to Otter Falls, this moisture was annoying. But I cannot blame the annoyance entirely on not having a rain cover -- the kind of constant rain I experienced has a way of creeping in despite the best counter measures.

The larger determiner on the rain cover dilemma is how to best use the Atmos. On short day trips like Squak Mountain, it was overkill. I literally stuffed items into the bag with no intention of using them just to give the bag some weight and bulk (I like to pack extra water because it's easy to get rid of during the course of the hike if I want to lighten up quickly). I should remind the reader that I am a minimalist, which influences my opinion of the pack as overkill on a day hike. I gravitate towards a 600 cubic inch (10 L) pack for such excursions.

On trips like Mount Washington that warrant some emergency gear for warmth and traction, the Atmos fit my needs perfectly because it gave me options that a smaller pack cannot. Did I need to employ all of these options? No. But I appreciate the peace of mind from knowing that my gear is with me. Mount Washington, because of the snowy conditions, revealed some factors inherent to the design of the pack that I had not anticipated. I'm a short guy, so postholing in three feet (~90 cm) of snow caused a build up of snow between the anchor point of the waist belt and the back of the pack. As this snow compressed over time, I began to feel a solid wedge of snow at my kidneys. Remedying the situation was easy: one swift swipe from a friend. Once I knew to be aware of this issue, it never again got to the point of discomfort. The other revelation came at the top. I checked for signs of wear at the bottom of the pack (it was even with or below the top of the snow level during the postholing). To my disappointment, I noticed some scuffing of the material -- not a lot, but enough to surprise me.

Otter Falls showed me the limits of the Atmos. It barely held my 0 F (-17 C) sleeping bag (compressed in a stuff sack) and other emergency essentials. During my strategizing how to fit it all in, I once again found myself smiling at the sleeping pad straps. Without them, I would have been forced to a bulkier, less comfortable pack in order to fit it all. In fact, had I needed to take a tent (my partner in crime toted it), I would have left the Atmos at home due to space restrictions. I opted not to place my water reservoir in the dead space between the mesh of the back panel and the material of the bag (the Air Speed feature) in order to prevent any freezing that occurred that night. I was glad I made that decision, though having the reservoir in the main compartment did make contribute to the space restrictions. Despite being filled to capacity, it still wore comfortably. I forded those swollen streams without worrying about stability issues.

This discussion of uses brings me back to the rain cover dilemma. I would not use a rain cover on a day hike -- it's too much hassle for little reward. I would not use the Atmos again on a cold overnighter due to space -- which is the one scenario where a rain cover has a high reward for the hassle. On a late spring through early fall overnight trip that promised to be wet, I would both take the Atmos and want a rain cover. Perhaps I should add one to my wish list.

My experiences during the field testing phase left me less than impressed with some features, namely the need to use two hands in order to open the waist belt zippered pockets, the stow-on-the-go feature for my poles. My issue with the waist belt pockets remains. Does the cumbersome zipper position keep me from eating when I need to? No. It does make me pause when deciding to take a picture, weighing whether or not I really want to wrestle with the zipper for a particular shot. In the case of the stowing feature, I have had a change of opinion. Would I ever scramble with my poles jutting out horizontally? No. But I actually found myself relieved during the icy hike out from Otter Falls that I could easily ditch my poles (or quickly retrieve them).

Now on to those features that have continued to impress me: the comfortable fit, the stretch pockets, and the ventilation system. I had problems early on with the fit, especially along my waist. I chalk these problems up to user error -- I did not have the belt cinched tightly enough, nor had I adjusted the rest of the suspension system correctly. During the long-term testing phase, I made the proper adjustments and had no problems. The stretch pockets on the sides and the front saved me when space was an issue. I stowing my rain jacket and other drenched gear in the front pocket during the Otter Falls trip. The limit to the side pockets is that they have openings on the sides in order to add versatility to those folks who prefer water bottles. Since I use a hydration reservoir, I found myself wishing that the side pockets lacked these holes. But when it comes to securing my poles to the sides of the bag, I appreciate the stretch fabric of these pounches. Combined with the straps inside (or outside, depending on your preference), these pockets make my poles impervious to movement despite passing branches or precarious angles. In terms of the ventilation system, the key seems to be the Air Speed feature. I have never been so unaware of my sweaty back (as disgusting as they statement is).

SUMMARY

The Atmos is not built for all conditions. In fact, it fills only a couple of niches. One of those niches is day hikes that demand emergency gear. The Atmos frees me from the debate over what to leave behind. Another niche is light weight overnighters. As long as the sleeping bag packs down to the size of a standard Nalgene bottle or a little bigger, the Atmos provides ample room for the other essentials. Can it be stretched for cold weather camping? Yes, as long as I have a buddy coming who is willing to carry more than his fair share.

CONTINUED USE

Aside from what I've already mentioned, I may use it during some of my mountain biking overnighters during the summer -- it allows me to have a full range of head motion with a helmet on. Some of these trips will even transition to rock scrambling and low class climbing, scenarios which are well suited to the Atmos in that it does not limit my range of motion or severely alter my center of gravity. As a whole, the Atmos has only confirmed my appreciation for Osprey's packs.

My thanks go to Osprey and backpackgeartest.org for the opportunity to experience the Atmos 35.

Product tested and reviewed in each Formal Test Report has been provided free of charge by the manufacturer to BackpackGearTest.org. Upon completion of the Test Series the writer is permitted to keep the product. Owner Reviews are based on product owned by the reviewer personally unless otherwise noted.